Electromagnetic Wave Prob. (Is this a typo/error?)

[WolfOfTheSteps]

Electromagnetic Wave Prob. (Is this a typo/error??)

http://img519.imageshack.us/img519/4536/errorko2.th.jpg

This is the book's solution to an E&M problem. I typed in the part that is enclosed by a red box.

Am I not correct, and the "official" solution is wrong?!?

It's basically a math error, but I can't believe they made it.

 

[Dick]

Yes, the modulus is clearly 'a'. Who is 'they'?

 

[WolfOfTheSteps]

Yes, the modulus is clearly 'a'. Who is 'they'?

The book's author! (I should have said "he")

 

[cristo]

The book's author! (I should have said "he")

It's not necessarily the books author that writes the solutions-- it was probably one of his grad students! Anyway, books have loads of typos in; it's nothing new!